n Mongredien's _Trees and Shrubs_, and Hooker's
_British Flora_, the fruits of no less than sixty-eight, or rather more
than half, are red, forty-five are black, fourteen yellow, and seven
white. The great prevalence of red fruits is almost certainly due to
their greater conspicuousness having favoured their dispersal, though it
may also have arisen in part from the chemical changes of chlorophyll
during ripening and decay producing red tints as in many fading leaves.
Yet the comparative scarcity of yellow in fruits, while it is the most
common tint of fading leaves, is against this supposition.

There are, however, a few instances of coloured fruits which do not seem
to be intended to be eaten; such are the colocynth plant (Cucumis
colocynthus), which has a beautiful fruit the size and colour of an
orange, but nauseous beyond description to the taste. It has a hard
rind, and may perhaps be dispersed by being blown along the ground, the
colour being an adventitious product; but it is quite possible,
notwithstanding its repulsiveness to us, that it may be eaten by some
animals. With regard to the fruit of another plant, Calotropis procera,
there is less doubt, as it is dry and full of thin, flat-winged seeds,
with fine silky filaments, eminently adapted for wind-dispersal; yet it
is of a bright yellow colour, as large as an apple, and therefore very
conspicuous. Here, therefore, we seem to have colour which is a mere
byproduct of the organism and of no use to it; but such cases are
exceedingly rare, and this rarity, when compared with the great
abundance of cases in which there is an obvious purpose in the colour,
adds weight to the evidence in favour of the theory of the attractive
coloration of edible fruits in order that birds and other animals may
assist in their dispersal. Both the above-named plants are natives of
Palestine and the adjacent arid countries.[142]

_The Colours of Flowers._

Flowers are much more varied in their colours than fruits, as they are
more complex and more varied in form and structure; yet there is some
parallelism between them in both respects. Flowers are frequently
adapted to attract insects as fruits are to attract birds, the object
being in the former to secure cross-fertilisation, in the latter
dispersal; while just as colour is an index of the edibility of fruits
which supply pulp or juice to birds, so are the colours of flowers an
indication of the presence of nectar or of pollen